MODFLOW Simulation Research Articles

Assessment of urbanization‐related groundwater flooding process via Visual MODFLOW modeling: A case study for the northern part of Almaty city, Kazakhstan

AbstractGroundwater flooding might be triggered by disregarding hydrogeological processes during urban area development. Such flooding might result in public disruption, engineering infrastructure destruction, and general damage to natural and human environments, as in the northern part of Almaty city. A MODFLOW groundwater flow model was used to simulate and quantitatively assess the changes in hydrogeological conditions affecting the groundwater flooding process. A field study of the Akbulak micro‐district research site showed that groundwater flooding occurred in its center owing to a water table hillock with a total area of 0.07 km2 and groundwater levels ranging from 1.2 to 0.25 m below the ground surface. The MODFLOW simulation suggested that this water table hillock developed from runoff, which, owing to a decrease in natural infiltration across an urbanized area, accumulated in low‐elevation areas and infiltrated. This runoff accumulation effect may be up to eight times the annual average precipitation amount. Once in local sub‐basins, larger runoff volume infiltrates into an underlying aquifer water table that is already high, might cause groundwater flooding in populated areas. The Almaty scenario simulation confirmed the field observations, suggesting that the clogging of the Karasu‐type stream has concentrated runoff to low‐elevation areas and is the leading cause of flooding.

Optimum identification of aquifer parameter zone structures using the SHuffled Ant Lion Optimization approach considering general form of the Voronoi tessellation

A new simulation–optimization approach is proposed for solving the inverse parameter structure identification problems in groundwater systems. In the simulation part of the proposed approach, the numerical groundwater flow process is simulated by using MODFLOW. Parameter structures of the aquifer system are identified by partitioning the flow domain into a finite number of zones employing the general form of the Voronoi tessellation (VT). This MODFLOW and VT-based simulation model is then integrated into an optimization model where the SHuffled Ant Lion Optimization approach (SHALO) is used. This work is the first application of SHALO by considering the general form of the VT zonation approach for solving the inverse groundwater parameter structure identification problems. The applicability of the proposed simulation–optimization approach is evaluated on a hypothetical aquifer model in the literature. This evaluation is conducted by solving the same problem using Ant Lion Optimization (ALO) and its improved version, the self-adaptive ALO (saALO) for the same conditions. Furthermore, the identified results are compared with those obtained using harmony search (HS) and hybrid genetic algorithm (hybrid GA) based solution approaches in the literature. The obtained results indicated that the proposed approach provided better identification results than ALO, saALO, HS, and hybrid GA in terms of different evaluation metrics.

Using MODFLOW to Model Riparian Wetland Shallow Groundwater and Nutrient Dynamics in an Appalachian Watershed

Simulating shallow groundwater (SGW) flow dynamics and stream–SGW interactions using numerical modeling tools is necessary to develop a mechanistic understanding of water flow systems and improve confidence in water resource management practices. A three-dimensional (3D) SGW flow model was developed for a riparian wetland in a mixed forest and agricultural catchment in West Virginia (WV), Appalachia, USA, using a Modular 3D Groundwater Model (MODFLOW). The MODFLOW simulation was calibrated in steady (R2 = 0.98, ME = −0.21, and RMSE = 0.77), transient state (R2 = 0.97, ME = −0.41, and RMSE = 1.28) and validated (R2 = 0.97, ME = −0.28, and RMSE = 1.05) using observed SGW levels from thirteen nested piezometers under steady and transient states. An experimental MT3D transport scenario was developed to show the lateral transport of NO₃-N from the aquifer to stream cells. Relatively stable SGW head distribution was observed. In the downstream reach, SGW discharge varied from 948 m3/day to 907 m3/day in 2020, with creek seepage ranging from 802 m3/day to 790 m3/day. Similarly, SGW input to the stream ranged from 891 m3/day to 978 m3/day, while creek seepage ranged from 796 m3/day to 800 m3/day in 2021. In upstream reaches, losing stream conditions were observed in January, June, and September 2020 and January to April 2021, while gaining stream conditions prevailed during other months. Thus, an approximately monthly alternating gaining–losing stream condition was observed in the upstream area. An experimental MT3D transport scenario resulted in an advection–dispersion scenario, showing a cumulative loss of 947 g of NO3-N from SGW to the stream. Denitrification accounted for the cumulative loss of 1406 g of NO3-N from SGW, surpassing 639 g of nitrate from the SGW to the stream during the study period. Additionally, particle tracking using MODPATH indicated a long residence time for SGW nutrients, affirming the efficiency of nitrogen transformation through denitrification. This study is among the first to simulate hydrologic and nutrient interactions in riparian wetlands of a mixed land use catchment in the Appalachian region of the northeastern United States. The results better inform water resource management decisions and modeling efforts in the Appalachian region and similar physiographic regions globally.

Groundwater flow simulation for artificial recharge: a GIS, remote sensing, and MODFLOW integration

ABSTRACT Groundwater (GW) emerges as a sustainable resource to meet water demand, yet current GW reservoirs fall short of projected population needs. Artificial GW recharge, bolstered by Geographical Information System (GIS) and Remote Sensing (RS) technologies, stands out as a pivotal solution. Examining Aurangabad district in Maharashtra, India the study uncovers distinct challenges: Aurangabad faces escalating water demand due to population growth, leading to GW over exploitation. Leveraging hydrogeological parameters, rainfall analysis, and GW availability, the study proposes tailored GW recharge techniques. Utilizing MODFLOW simulation, the study explores diverse recharge rates and existing GW availability, showcasing promising results. Integration of stream augmentation, bladder pillow tank methods, and dug well recharge is examined via GIS and RS techniques. Simulation outcomes project significant GW level increases (11.55–23.70 m) with varying recharge rates, effectively meeting region-specific water demand projections. The findings underscore the imperative of sustainable water management practices and technological advancements in addressing water scarcity crises.

Contribution of Groundwater to River Discharge in the Mampang Sub-watershed

Water is a necessity of human life. In fulfilling this need, the use of groundwater is often used. Groundwater is a non-renewable resource. Jakarta is a city traversed by many rivers and has a morphological dependence on the upstream watershed (DAS) in the Jabodetabek Region. The research location is in the Mampang Sub-watershed, which is in the Jakarta and Depok areas. The Mampang sub-watershed is geographically located at 106°48'44" - 106°49'59" East Longitude and 6°15'4" - 6°22'17" South Latitude. The problem in the research of the Mampang Sub-watershed often experiences floods every year with a height of between 10 cm - 50 cm. The aim of the study was to determine the groundwater-surface water interaction during a flood event at the study site. The method used is by collecting primary data and secondary data, then simulating using SWAT (Soil and Water Assessment Tools) and SWAT-MODFLOW. The SWAT MODFLOW simulation results obtained 874 river grids with Groundwater Surface Water Exchange Rates (GWSER) values in February 2020 between 52 m3/day to 353 m3/day and in September 2019 between -74 m3/day to 26 m3/day. The contribution of groundwater can be analyzed by comparing the river discharge in a certain month with the GSWER value for that month. The contribution of groundwater to the monthly peak discharge of the river at the study site ranges from 0.24% to 5.27%, and the average contribution of groundwater is 2.48%.

Study on the material characteristics and barrier mechanism of magnesium potassium phosphate cement/hydroxyapatite cutoff walls for fluoride contamination in phosphogypsum waste stacks

• Magnesium potassium phosphate cement using hydroxyapatite as admixture was prepared as a kind of new cutoff wall material. • The cutoff walls have good adsorption performance for fluorine and could meet the engineering requirements. • Internal structural parameters were analyzed through the pore-scale modeling. • The effect of the cutoff walls for controlling fluorine at 7300 days was simulated by Visual MODFLOW. Large quantities of fluoride were leakaged from the phosphogypsum wastes with rainfall and weathering, which has affected the groundwater environment. As a common engineering material, magnesium potassium phosphate cement (MKPC) with high strength and low permeability was applied in barriers to control the diffusion of contaminants in the groundwater. As an effective fluoride adsorbent, this paper selected hydroxyapatite (HAP) as the admixture for magnesium potassium phosphate cement (MKPC) to prepare the cutoff walls. To explore the feasibility of the cutoff walls applying for fluoride contaminants control, studies were carried out through investigating the appropriate material ratio, adsorption property, migration characteristics, microstructure and engineering performance of MKPC-HAP. Based on the permeability coefficient, compressive strength and adsorption property, the molar mass ratio of magnesium to phosphorus in MKPC and the addition of HAP in the total dry material were determined to be 3:1 and 20 %, respectively. The compressive strength after curing for 7 days was 27.51 MPa and permeability coefficient was 1.904 × 10 −9 m/s. Furthermore, the effective diffusion coefficient and the seepage velocity of fluoride with concentration of 100 mg/L were 7.376 × 10 −8 cm 2 /s and 2.21 × 10 −8 m/s, respectively. The Lattice Boltzmann method (LBM) was applied to simulate the distribution of flow field inside the MKPC-HAP cutoff walls and the connected porosity of MKPC-HAP was 5.12 %. Finally, the service life varied from 12 to 22 years when the fluoride concentration being 50 mg/L with the 1 m cutoff wall thickness. Visual Modflow simulation showed that the migration distance of fluoride was 820 m without the cutoff walls, while it was 402 m after setting the cutoff walls over 7300 days.

Minimizing Errors in the Prediction of Water Levels Using Kriging Technique in Residuals of the Groundwater Model

Groundwater monitoring and water level predictions have been a challenging issue due to the complexity of groundwater movement. Simplified numerical simulation models have been used to represent the groundwater system; these models however only provide the conservative approximation of the system and may not always capture the local variations. Several other efforts such as coupling groundwater models with hydrological models and using geostatistical methods are being practiced to accurately predict the groundwater levels. In this study, we present a novel application of a geostatistical tool on residuals of the groundwater model. The kriging method was applied on the residuals of the numerical model (MODFLOW) generated by the TWDB (Texas Water Development Board) for the Edwards–Trinity (Plateau) aquifer. The study was done for the years 1995 through 2000 where 90% of the observation data was used for model simulation followed by cross-validation with the remaining 10% of the observations. The kriging method reduced the average absolute error of approximately 31 m (for MODFLOW simulation) to less than 5 m. Furthermore, the residuals’ average standard error was reduced from 9.7 to 4.7. This implies that the mean value of residuals over the entire period can be a good estimation for each year separately. The use of the kriging technique thus can provide improved monitoring of groundwater levels resulting in more accurate potentiometric surface maps.

An Integrated Aquifer Management Approach for Aridification-Affected Agricultural Area, Shengeldy-Kazakhstan

Ongoing water-resource depletion is a common trend in southeastern Kazakhstan and in most of Central Asia, making the use of drainage water for freshwater preservation and groundwater recharge a key strategy for sustainable agriculture. Since the Ily River inflow began to decrease, groundwater levels in the Shengeldy study area site have fallen below the drainage pipes. As such, our main research hypothesis was that owing to drainage infiltration, the regional shallow aquifer can be used as an effective additional water source for moistening crop root systems during the irrigation period. The MODFLOW groundwater flow model was used to simulate and quantitatively assess the combined hydrogeological and irrigation conditions of artificial groundwater recharge both from the subsurface drainage and as an additional source for irrigation. The field study showed that the additional groundwater table elevation will reach approximately 1.5 m under the field drainage system and that the additional groundwater recharge influence zone will develop up to 300–350 m from the drains. The MODFLOW simulation together with full-scale experimental studies suggests that under certain conditions drainage water can be applied both as an additional source of irrigation and for aquifer sustainable maintenance.

A framework for the assessment of qualitative and quantitative sustainable development of groundwater system

AbstractThe groundwater mitigation issues and moving toward sustainable quality and quantity conditions of the aquifers are primary water resources management objectives in arid and semi‐arid regions. A framework is required to assess groundwater restoration strategies' impacts on the aquifer's qualitative and quantitative sustainability. In this study, two new indices are introduced to evaluate the state of aquifer sustainability. The aquifer quantity restoration index was determined by using the results of the MODFLOW, considering the differences between the simulated and the desired water levels and the storage volumes for restoration scenarios, and the percentage of obtaining the desired level at the end of the simulated period. The aquifer quality restoration index was defined based on the DRASTIC‐LU aquifer vulnerability and the percentage of the desired total dissolved solids (TDS) goals at the end of the simulated period using the Bayesian networks model. Six restoration groundwater scenarios in 10 years were assessed to examine both proposed indices. Scenarios are comprised of a one to 3.5% reduction in agriculture groundwater withdrawal. The aquifer quantitative restoration index resulting from the MODFLOW simulation indicated that 2.5% of the decrease in groundwater withdrawal satisfied the aquifer's sustainability. Furthermore, the qualitative sustainability index showed that the reduction in groundwater withdrawal has enormous impacts on the aquifer's central area and marginal parts, where the groundwater is dramatically over‐exploited. Indices proposed can be utilized for the assessment of achieving sustainable management in groundwater by restoration scenarios.

Enhancement of sustainable agricultural production system by integrated natural resources management framework under climatic and operational uncertainty

Constant decline of freshwater reserve poses a major challenge for coastal agricultural systems. The present study focuses on the integrated land and water resources management framework under operational and climatic uncertainties to achieve sustainable agricultural production in a tropical coastal river basin. To capture the operational and climatic uncertainties, Grey Linear Programming (GLP) and Acceptability Constrained Linear Programming (ACLP) optimization models were developed. GLP can consider both climatic and operational uncertainties. However, ACLP can accommodate operational uncertainty only. Groundwater model was coupled within the optimization models (GLP and ACLP) by a grey response matrix. The SWAT estimated recharge rates were utilized in the MODFLOW model as the groundwater flux. The calibrated (R2 = 0.80) and validated (R2 = 0.84) groundwater flow simulation model was utilized to generate the grey response matrix. The eight plausible scenarios were tested for GLP (Scenarios I, II, III, IV, V, VI, VII, VIII) and ACLP (Scenarios Ia, IIa, IIIa, Iva, Va, VIa, VIIa, VIIIa) with groundwater table fluctuation (GWTF) method and grey response matrix as drawdown constraint. A reduction in net annual return was observed in Scenarios III and IV (with grey response matrix) in comparison to Scenarios I and II (with groundwater table fluctuation) under any change in crop yield. Decrease was more prominent for Rabi (winter) season compared to Kharif (monsoon) season. Futuristic Scenarios (V, VI, VII, VIII) considering crop yield reduction showed a possible change required in cropping pattern (specifically rice area reduction in Kharif Season). ACLP model results showed similar trends. Results suggest that the GWTF method overestimates the groundwater availability compared to the physically based simulation model. Obtained land and water resources management plans were cross-validated for the safe yield limit using MODFLOW simulation model.

DSSAT-MODFLOW: A new modeling framework for exploring groundwater conservation strategies in irrigated areas

Groundwater models are often used to assess the impact of climate or management strategies on groundwater resources in arid and semiarid regions of the world. However, these models do not account for crop growth and crop yield, and thus cannot be used for evaluating long-term impacts of climate and management strategies on water use efficiency and farm profitability of agricultural systems while managing the aquifers sustainably. This study presented a linkage between DSSAT, an agronomic model, and MODFLOW, a groundwater flow model. The linkage between these two models occurred on an annual basis, with rates of irrigation and deep percolation from an ensemble of field-scale DSSAT simulations converted to pumping rates and recharge rates for the MODFLOW simulation. MODFLOW simulated groundwater head, which can be used to update saturated thickness and thereby well capacities for each pumping well in the model domain. Simulated well capacities were then used to constrain irrigation applications in the DSSAT simulations during the following growing season. Python scripts were used to convert output from one model to input files for the other model. The DSSAT-MODFLOW modeling system was applied to the Ogallala aquifer underlying Finney County, Kansas, a region experiencing significant groundwater depletion due to irrigation practices, and was tested against observed water table elevation and crop yield. Over a decadal period, well capacity decreased by > 50 % for many pumping wells in the county. A no-irrigation scenario for this same time period resulted in average water table elevation increasing by 2 m, but also a 70 % decline in crop yield. Additional work is needed to balance groundwater conservation with crop yield. The DSSAT-MODFLOW modeling system can be used in regions worldwide to assess changes in irrigation technologies, crop selection, and climate change adaptation strategies.

Hydraulic performance evaluation of a quasi-two dimensional constructed wetland microcosm using tracer tests and Visual MODFLOW simulation

Hydraulic conditions of constructed wetlands (CWs) are crucial to pollutant removal and are influenced by factors such as influent loading rates, influent or effluent position or porous media size. The performance evaluation of CWs in real application, however, is difficult and a visualization analysis is difficult due to the black-box effect. In this paper, a nonopaque microcosmic horizontal subsurface flow constructed wetland (HSSFCW) reactor was built in the laboratory for an efficient and intuitive assessment of the influences of such parameters on the hydraulic performance of CWs. Chloride tracer tests were carried out to obtain parameters on hydraulic performance by considering hydraulic loading rates and different flow inlet-outlet configurations, while dye tracer tests were designed for the visualization of solute transport and diffusion. In parallel, an identical design of the HSSFCW reactor was modeled using the Visual MODFLOW (VM) software in order to detect the tracer movement and solute concentration field. Results show that the inflow rate and the inlet-outlet configuration have significant impacts on the hydraulic performance of a CW influencing RTD curve shape, flow path, dead zone distribution and hydraulic efficiency. The dead zone and flow path have been visualized and analyzed by comparing the dye tracer experiments of VM solute concentration field and particulate path-line tracking. In addition, the feasibility and reliability of the VM simulation has been verified. The application of VM in this study has been robust indicating a possible application for further investigations on the influencing factors of real CWs.

Groundwater discharge downstream of an arid inland river in Northwestern China

Nalenggele River is an inland river located in the arid, fragile ecological environment area in Northwestern China. Groundwater discharge to the river can significantly impact the ecologic environment in the Nalenggele River basin, but few hydrogeological studies have been conducted in the inland arid basin. In this paper, two sections were chosen to analyze the groundwater discharge in the downstream of Nalenggele River. Section I–I′ is located in the west of the downstream of this river, while section II–II′ is in the east. Two methods were used to calculate the discharge in section I–I′: Darcy's law and Modflow simulation. In these two methods, the vertical hydraulic conductivity of the stream sediment is a key parameter, which was determined by a falling-head permeameter test in the river. The results show that the groundwater discharges by the above two methods are very close to the results of a previous study by the 222Rn mass balance method. This is the first attempt to use a field test method to obtain the vertical hydraulic conductivity and the hydraulic gradient, and to illustrate the groundwater discharge in the downstream of Nalenggele River in Northwestern China by classic methods.

An agent-based-nash modeling framework for sustainable groundwater management: A case study

An agent-based-Nash modeling framework has been developed to find a sustainable solution for groundwater management in Daryan Aquifer, Fars Province, Iran. This framework also includes a MODFLOW simulation model, an Artificial Neural Network (ANN), and a Non-dominated Sorting Genetic Algorithm-II (NSGA-II) optimization model. Groundwater state was simulated using MODFLOW and it was calibrated based on the measured data provided by Regional Water Organization (RWO) of Fars Province. In order to reduce the computational time, an ANN was trained and validated based on the input-output data of the MODFLOW model to estimate groundwater level. The validated ANN was linked to a nonhomogeneous elitist NSGA-II multi-objective optimization model to find a Pareto optimal front among the three objectives of reducing irrigation water deficit, increasing equity in water allocation, and reducing groundwater drawdown, as the objectives of the three main groundwater resource stakeholders; farmers, the government executive sector, and the environmental protection institutes. The Nash bargaining model was applied to the optimal solutions in order to find a compromise among the stakeholders. Social influential factors in the study environment, and policy mechanisms to encourage agents to cooperate with the management decisions were implemented in the agent-based model. These factors include training, incentives, penalties, and social norming (neighbors' impacts), as well as considering the executive and judicial systems. After application of the agent-based model, computed optimum solutions were modified according to social conditions. Finally, the Nash bargaining model was used again to find a compromise among modified optimal objectives of the stakeholders. Implementation of this solution led to 58.3% less water extraction and approximately 3m water level uplift.

Mine-Water Flow between Contiguous Flooded Underground Coal Mines with Hydraulically Compromised Barriers

Groundwater flow entering closed contiguous underground coal mines may be strongly influenced by leakage across inter-mine barriers. This study examines a complex of multiple closed and flooded mines that developed into a nearly steady-state groundwater flow system within 10 to 50 years after closure. Field water-level observations, mine geometry, barrier hydraulic conductivity, recharge rates, and late-stage storage gains were parameterized to match known pumping rates and develop a fluid mass balance. Vertical infiltration (recharge and leakage) estimates were developed using a depth-dependent model based on the assumption that most vertical infiltration is focused in areas with <75 m of overburden. A MODFLOW simulation of the nearly steady-state flow conditions was calibrated to hydraulic heads in observation wells and to known pumping rates by varying barrier hydraulic conductivity. The calibrated model suggests significant head-driven leakage between adjacent mines, both horizontally through coal barriers and vertically through inter-burden into a shallower mine in an overlying seam. Calibrated barrier hydraulic conductivities were significantly greater than literature values for other mines at similar depths in the region. This suggests that some barriers may be hydraulically compromised by un-mapped entries, horizontal boreholes, or similar features that act as drains between mines. These model results suggest that post-mining inter-annual equilibrium conditions are amenable to quantitative description using mine maps, sparse observation-well data, accurately estimated pumping rates, and depth-dependent vertical infiltration estimates. Results are applicable to planning for post-flooding water-control schemes, although hydraulic testing may be required to verify model results.

UNDERGROUND WATER IN OPEN PIT MINING AT MAE MOH MINE OF THAILAND

The groundwater problem at Mae Moh mine has drawn attention as the mining excavation goes deeper, thus resulting in detailed investigation of hydrogeological condition. One of the problems facing the mining is floor heave influenced by groundwater. The control of groundwater pressure in deep-seated aquifers with high elevation becomes important in the mining. In addition, the underground water at Mae Moh mine is naturally contaminated by arsenic. Therefore, the developments of 3D groundwater model of deep pit mine using Modflow simulation and the studies of underground water treatment are needed for the future planning. The predictive simulations were carried out for eight years (2007 to 2015). Because stability of the Mae Moh mine shows how can be closely linked to the water environment, this paper aims to report the field visits to the water related facilities of the mine, which were conducted during 2010-2013. The result reveals that the potentiometric head level is strongly increased, which might be a potential risk for the floor heave; thus, depressurization is required. Field measurements reveal pH level at 8 and a range of total dissolved solid (TDS) at 870-2020 ppm. Treatment efficiency shows that more than 95% of the arsenic can be successfully removed using ferric chloride.

Steady-state groundwater recharge in trapezoidal-shaped aquifers: A semi-analytical approach based on variational calculus

• A simple expression for areal recharge in trapezoidal aquifers is proposed. • The solution exhibits strictly close agreement with Modflow simulation results. • Isotropic and anisotropic aquifers are modeled. • The anisotropic case is characterized by comparatively lower water levels. • The triangular aquifer is regarded as a special case of the present formulation. This study presents a semi-analytical solution for steady groundwater flow in trapezoidal-shaped aquifers in response to an areal diffusive recharge. The aquifer is homogeneous, anisotropic and interacts with four surrounding streams of constant-head. Flow field in this laterally bounded aquifer-system is efficiently constructed by means of variational calculus. This is accomplished by minimizing a properly defined penalty function for the associated boundary value problem. Simple yet demonstrative scenarios are defined to investigate anisotropy effects on the water table variation. Qualitative examination of the resulting equipotential contour maps and velocity vector field illustrates the validity of the method, especially in the vicinity of boundary lines. Extension to the case of triangular-shaped aquifer with or without an impervious boundary line is also demonstrated through a hypothetical example problem. The present solution benefits from an extremely simple mathematical expression and exhibits strictly close agreement with the numerical results obtained from Modflow. Overall, the solution may be used to conduct sensitivity analysis on various hydrogeological parameters that affect water table variation in aquifers defined in trapezoidal or triangular-shaped domains.

Efficient Storage of Large MODFLOW Models

We present a methodology for storing the bulkier portions of a set of MODFLOW input and output files in a compressed binary format using the HDF5 library. This approach results in compression ratios of up to 99% with no significant time penalty. The highly compressed format is particularly beneficial when dealing with large regional models or Monte Carlo simulations. The strategy is focused on the list- and array-based portions of the input files including the cell property and recharge arrays, and is compatible with models containing parameters, including pilot points. The utilities are based on a modified version of the MODFLOW code and are, therefore, compatible with any standard MODFLOW simulation. We present used cases and instructions on how to use the utilities.

Groundwater Simulation System Study on Physical and Climatic properties on Kuwait Group Aquifer

In Kuwait natural resources of fresh water are very limited. Kuwait is situated in an arid coastal region characterized by high temperatures, low humidity, sparse precipitation rates, and high evaporation and evapotranspiration rates with no rivers or lakes. Therefore, Kuwait has always relied on other sources to secure freshwater to meet its growing demands. The aim of this study was to design a conceptual system to provide a sustainable water source at a feasible cost. The conceptual design system was developed to address the problem of water scarcity and sustainability in general, and specifically to represent the Kuwaiti water quality and quantity limitation problem.The conceptual design system consists primarily of utilizing brackish groundwater in conjunction with treated wastewater augmentation and a reverse osmosis unit for plant production, the simulation was chosen to represent the quasi-Kuwaiti environment data.The study considered two types of simulation models for the conceptual design system approach. These models are the lump model approach and the areal distribution model approach. The lump model approach was carried out through the construction of a simplified model approach utilizing the Visual Basic model. On the other hand, the areal distribution model approach was carried out through the utilization of the Visual MODFLOW and MT3D simulation model approach. This paper present a part of the study that directed to test the physical and climatic performance, and the durability of the conceptual design system, Visual basic, lump, model simulation approach was simulated for different ranges of hydrologic, hydrogeologic, and climatic parameters to determine the total power and treated wastewater consumption. From the performance test results, the increase in evapotranspiration had the highest increase effect on the system total power consumption per unit area and the highest increase effect on the treated wastewater consumption per unit area. On the other hand, the increase in the aquifer porosity had the least increase effect on both the total power consumption and the treated wastewater consumption by the system. In contrast, the hydraulic conductivity increase had no direct effect on either the total power consumption or on the treated wastewater consumption per unit area.

Optimal management for groundwater of Nubian aquifer in El Dakhla depression, Western Desert, Egypt

El Dakhla depression occupies a structurally localized depression at 100 to140 m (amsl), below a 400 m escarpment bordering the Libyan Plateau, Western Desert of Egypt. In this area, groundwater of the Nubian Sandstone aquifer is the unique source of fresh water. The increasing demand of groundwater in El Dakhla depression has resulted in an indiscriminate exploitation of this source causing environmental hazards such as decline of groundwater levels. In this paper, the study of this problem is conducted. The methodology introduced in this paper includes application of mathematical and genetic algorithm (GA) techniques. The proposed model of optimization is based on the combination of the MODFLOW simulation with GA. The performance of the proposed model is tested on groundwater management problem (maximization of total pumping rate from Nubian aquifer at steady-state). The results of the simulation show that the present groundwater extractions (511783 m3/day) will affect the groundwater flow patterns in the northeastern areas of El Dakhla depression causing a significant head decline of about 26 m in some wells at the year 2050. The increase of the groundwater extractions from the concerned aquifer by 25% (126355 m3/day) will cause a great head decline of about 60 m in some wells and accordingly a cone of depression around the wells in the year 2050. In addition, the GA solutions solve these management problems in the groundwater of Nubian aquifer. The results show that under the increasing of pumping rate by 25% (which equalizes an increase in the cultivated area by 6000 ha), the optimal pumping rate and drawdown range from 638137.9 to 595977.9 m3/day and from 4.292 to 10.36 m respectively. This result seems to be the best for optimal management of groundwater. Key words: Hydrogeology, Nubian Sandstone aquifer, optimal management, genetic algorithm, MODFLOW, Dakhla depression, Egypt.